#include "stdio.h"
//指针调用交换数值
void f7(int *x,int *y)
{
  int tmp;
  tmp = *x;
  *x = *y;
  *y = tmp;
}
int main()
{
int m = 10;
int n = 20;
f7 (&m,&n);
printf ("%d %d",m,n);
}